Work feeding mechanisms for sewing machines



Sept. 16, 1969 w 5; GREENWOOD, JR" ET AL 3,467,039

WORK FEEDING MECHANISMS FOR SEWING MACHINES as 2 M INVENTORS WIIIICIm 8. Greenwood Jr.

BY and Andrew Visuggio WITNESS: WM Maw/m ATT NEY Sept. 16, 1969 w. s. GREENWOOD, JR., ETAL 3,467,039

WORK FEEDING MECHANISMS FOR SEWING MACHINES Filed Nov. 20, 1967 2 Sheets-Sheet 2 e INVENTORS William 8. Greenwood Jr BYond Andrew Visoggio WITNESS: 1 am;- ana/0:! AT ORNEY United States Patent 3,467,039 WORK FEEDING MECHANISMS FOR SEWING MACHINES William S. Greenwood, Jr., Nutley, and Andrew Visaggio, Wayne, N.J., assignors to The Singer Company, New York, N .Y., a corporation of New Jersey Filed Nov. 20, 1967, Ser. No. 684,184 Int. Cl. Db 27/02, 49/00 US. Cl. 112--203 5 Claims ABSTRACT OF THE DISCLOSURE A work feeding mechanism for a sewing machine is disclosed in which a work feeding element is maintained at a constant elevation and is imparted movements only in the line of feed, while a small work supporting platform disposed substantially completely within the vertical projected outline of the presser foot is alternately raised vertically above the level of the feeding element and lowered beneath the level of the feeding element during the feed movements thereof.

BACKGROUND OF THE INVENTION Conventional fourmotion work feeding mechanisms for sewing machines provide a feed dog which is movable not only vertically into and out of engagement with the work fabric through slots in a stationary throat plate, but also horizontally in a feeding stroke while elevated into engagement with the work fabric and in a return stroke while lowered. In these feed mechanisms, the feed dog is raised in opposition to the presser foot at the beginning of each feed stroke and inertia causes the presser foot to continue rising, thus diminishing the effectiveness of the feed.

Work feed mechanisms are also known in which the feed dog remains at a constant level moving only in feed and return stitches, while the entire throat plate is shifted vertically. The movement of the throat plate in an area where an operator is frequently manipulating the work can be bothersome to the operator and detrimental to proper guiding of the work to the stitching point.

SUMMARY OF THE INVENTION It is an object of this invention to provide a work feeding mechanism in which the work feeding element remains at substantially constant level and is moved in the direction in which the work is to be fed, and in which the sewing machine throat plate is also supported at a constant level. A platform located adjacent to the work feeding element and disposed substantially completely within the vertical projection of the presser foot is shiftably supported for movement beneath the level of the work feeding element to expose the element for effective work feeding motion and for movement above the level of the work feeding element in opposition to the presser foot to provide for periods of ineffectiveness of the work feeding element. Since the presser foot will be raised by the platform at the beginning of the periods .of ineffectiveness of the work feeding element, any overthrow by reason of inertia occurring in the presser foot will not be detrimental to the work feed. Moreover, the operator guiding work in the immediate vicinity of the stitching point will manipulate the work against a stationary throat plate.

DESCRIPTION OF THE DRAWINGS With the above and additional objects and advantages in view as will hereinafter appear, this invention comprises the devices, combinations, and arrangements of parts hereinafter described and illustrated in a preferred embodiment illustrated in the accompanying drawings in which:

FIG."1 is a top plan view of a fragment of a sewing machine bed including portions of a conventional sewing machine feed advance and feed lift rock shafts in the bed and having the feed mechanism of this invention applied thereto;

FIG. 2 is a sectional view taken substantially along line 22 of FIG. 1 and including the sewing machine presser foot and needle;

FIG. 3 is a cross sectional view taken substantially along line 3-3 of FIG. 2 and including the sewing machine presser foot, and

FIG. 4 is an exploded perspective view of the work feeding mechanism of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIGS. 1 and 2 of the drawings, fragments of a sewing machine bed 11 are illustrated including a work supporting top surface 12 of the bed. Indicated at 13 is an access opening in the work supporting top surface of the bed which access opening may be closed by a slide cover plate 14. The access opening is conventional in sewing machines to expose a loop taker 15 which is carried in the bed and cooperates in the forming of stitches with a reciprocating needle 16 carried above the bed. In the present invention, the access opening also serves as an opening through which the work feed mechanism extends from within the sewing machine bed into engagement with the work fabrics which are on the Work supporting top surface of the bed.

The work feeding mechanism of this invention is supported and driven by a feed advance rock shaft 20 and a feed lift rock shaft 21 both carried in substantial parallelism in the bed beneath the work supporting top 'surface. The feed advance and feed lift rock shafts are preferably each sustained on pintles carried in the bed; there being illustrated in FIG. 1 one such pintle 22 engaging one extremity of the feed advance rock shaft 20. For the feed lift rock shaft 21, a pintle 23 is illustrated in FIG. 1 being threaded in the bed 11. The pintle 23, however, does not directly engage the feed lift rock shaft. A feed lift rock arm 24 has an elongated hub 25 formed with a bore 26 which accommodates the feed lift rock shaft, the hub being secured thereto by a set screw 27. Also accommodated in the hub bore 26 is a pilot portion 28 of a stud formed with a shouldered cylindrical bearing portion 29 and an enlarged head 30 which engages the pintle 23. The stud is locked in the feed lift rock arm hub 25 by means of a set screw 31.

Rotatable on the cylindrical bearing portion 29 of the stud is a guide block 32 which is embraced by a bifurcated portion 33 of a feed bar 34. The feed bar is pivotally connected by a bolt 35 between the upstanding rock arms 36 fast on the feed advance rock shaft 20. Secured to the feed bar 34 as by screws 37 is a feed dog 38 having work engaging surfaces which, as illustrated in the accompanying drawings, are preferably in the form of three spaced bars 39, 40 and 41 which may be formed with work engaging teeth although other forms of the feed dog may be employed with this invention as will be apparent.

With the construction and arrangement of the feed bar as disclosed above, oscillating movement of the feed advance rock shaft will impart reciprocating movement to the feed dog and the work engaging surfaces of the feed dog will reciprocate in a substantially fixed plane rela tively to the sewing machine bed. Oscillation of the feed lift rock shaft will have no influence on the motion of the feed dog.

The feed lift rock arm 24 terminates in a clevis 45 between the arms of which a substantially vertical link 46 is pivoted on a pin 47. Beneath the clevis the link 46 is pivotally connected by a pin 48 to an anchor link 49 sustained on a shouldered fulcrum bolt 50 secured in the sewing machine bed. Preferably the radius arm of the anchor link, i.e., the distance between the axis of the fulcrum bolt 50 and the pin 48 is equal to the radius arm of the feed lift rock arm 24 i.e., the distance between the axis of the feed lift rock shaft and the axis of the pin 47, so that the vertical link 46 will partake of substantially rectilinear translatory movement for small angular oscillations of the feed lift rock shaft 21.

Pivoted on a pin 51 set in the vertical link 46 above the feed lift rock arm clevis is a carrier bracket 52 which is formed at the top with a pair of spaced arms 53 of which the outer edges 54 are outwardly beveled as best illustrated in FIG. 3.

Slidable on the spaced arms of the carrier bracket is a selected one of a plurality of work engaging platforms 55, 55A, 55B. These platforms differ only as to the shape of a needle accommodating aperture 56, 56A and 568, formed respectively in each platform the aperture 56 being especially suitable for straight stitch sewing, the aperture 56A, for zigzag sewing, and the aperture 56B, for chainstitch sewing. Only the platform 55 will be described in detail hereinbelow.

The platform 55 is formed with bifurcated arms 57, which as shown in FIG. 1 are interposed between the spaced bars 39, 40 and 41 of the feed dog. The undersides of the bifurcated arms 57 are undercut as indicated at 58 so as to conform with and key onto the beveled outer edges 54 of the carrier bracket. The forward portion of the platform 55 may be formed with serrations at each side to facilitate grasp by the operator during insertion of the platform into keyed relation on the carrier bracket and removal therefrom.

In FIGS. 2 and 3 is illustrated a conventional presser device in the form of a presser foot 60 having a sole plate 61 engageable with work fabrics to be stitched. The presser foot is secured by a screw 62 to a presser bar 63 carried in the sewing machine above the bed. As is conventional and as is illustrated by a fragment of a spring 64 in FIG. 2, the presser foot is biased toward the work support. As is conventional, the presser foot may be biased downward in a direction perpendicular to the work support or as shown in the drawings, at an angle of approximately 9 thereto. As illustrated in FIGS. 2 and 3, the work engaging bars 39, 40 and 41 of the feed dog extend Within the projected outline of the presser foot sole plate perpendicular to the fixed plane defined by the feed dog work engaging surfaces. The presser foot thus opposes the feed dog and cooperates therewith in advancing fabrics across the sewing machine bed.

Also as illustrated in FIGS. 2 and 3, the platform 55 when keyed onto the carrier bracket 52 is disposed substantially completely within the projected outline of the presser foot sole plate perpendicular to the feed dog work engaging surfaces.

In order that the platform 55 may move substantially in a path aligned with the direction in which the presser device is biased, the feed lift rock arm 24 and the anchor link 49 are each inclined upwardly at approximately 9 to match the 9 inclination of the presser foot bias.

As shown in FIG. 1, the slide cover plate 14 is formed with a slot 65 which embraces with slight clearance the feed dog bars 39 and 41 when the slide cover plate is closed. When the slide cover plate is retracted beyond the position illustrated in FIG. 1 the operator may grasp the serrated sides of the platform 55 and retract the platform from the carrier bracket as for exchange of the platforms. During sewing the slide cover plate 14 is preferably positioned so as to completely close the aperture 13 in the work supporting top of the bed.

The accompanying drawings do not illustrate an actuating mechanism for the feed advance and feed lift rock shaft for the reason that any conventional actuating mechanism for a four-motion work feeding mechanism may be adopted for such actuation. By four motion work feeding mechanism is meant that type of feed mechanism in which both horizontal and vertical feed and return motions and rising and falling motions are imparted to the feed dog. For example, the mechanism for actuating the feed advance and feed lift rock shaft of the four motion feeding mechanism of United States Patent No. 3,164,113 of S. J. Ketterer, Jan. 5, 1965, may be used to drive the feed advance and feed lift rock shafts of this invention. In operation, oscillation of the feed advance rock shaft 20 will impart horizontal reciprocating motion in a fixed plane to the feed dog 38, motion in one direction being a feed stroke and in the opposite direction a return stroke. In timed relation with the feed dog motion, the feed lift rock shaft may be oscillated to elevate the platform 55 above the level of the fixed plane of the feed dog teeth during the return stroke and to lower the platform below the level of said fixed plane during the feed stroke of the feed dog.

Since the platform is arranged substantially completely within the projected outline of the presser foot sole plate perpendicular to the fixed plane of the feed dog teeth, the operator in manipulating work fabrics as the fabrics are being stitched is not required to place her fingers in opposition to a moving portion of the sewing machine. The operator will, therefore, manipulate against the fixed surface provided by the slide cover plate 14.

It will be appreciated that the advantages provided by this invention will be obtained regardless of the type of work feeding element which is used so that in addition to a reciprocated feed dog as described in the preferred embodiment, other work feeding elements such as feed wheels, feed belts, and the like may be used.

With reference to the previously cited United States Patent No. 3,164,113, it will be noted that a thread pull off device for the bobbin thread of the lockstitch sewing machine has heretofore been associated successfully with four motion work feeding devices. In the present invention, although the conventional four motion work feeding mechanism has been departed from, a bobbin thread pull off mechanism is nonetheless provided having motions fully equivalent to those heretofore provided in association with the four motion work feeding mechanisms as is disclosed in the above referred United States Patent No. 3,164,113.

In the present invention, a bobbin thread pull-off mechanism is provided by a bell crank lever which is fulcrumed on the pivot pin 51 which supports the platform carrier bracket 52. A substantially horizontal arm 71 of the bell crank lever is formed with thread accommodating aperture 72 and it is this horizontal arm 71 which provides for bobbin thread pull off action. A vertical arm 72 of the bell crank lever 70 is engaged by a spring 74 which is anchored in the pivot pin 48. The spring 74 serves constantly to bias the horizontal arm 71 of the bell crank lever upwardly. Secured to the sewing machine bed 11 is a stop bracket 75 formed with a projection 76 which overlies the horizontal arm 71 of the bell crank. As the vertical link 46 supporting the platform 55 is reciprocated vertically during operation of the sewing machine and the fulcrum pin 51 of the bell crank lever 70 is reciprocated vertically with the link 46 the horizontal arm 71 of the bell crank bobbin thread pull-off lever 70 by virtue of contact with the projection 76 on the stop bracket 75 will be oscillated always in a direction opposite that of the movement of the platform 55. The pull-off action of the horizontal arm 71 upon the bobbin thread of a lockstitch sewing machine will, therefore, be practically indistinguishable from the action of the bobbin thread pull-off means described in the United States Patent No. 3,164,- 1 13.

Having thus set forth the nature of this invention, what is claimed herein is:

1. A work feeding mechanism for a sewing machine having a bed, and a presser device including a work engaging sole plate biased toward said bed, said work feeding mechanism comprising a work feeding element having Work engaging surfaces, means carried in said bed supporting said feeding element for movement with said work engaging surfaces constrained in a substantially fixed plane relatively to said sewing machine bed and extending within the projected outlines of said presser foot sole plate perpendicular to said fixed plane, said fixed plane being substantially parallel to said work engaging sole plate, a work engaging platform extending adjacent to said feeding element work engaging surfaces and disposed substantially completely within the projected outlines of said presser foot sole plate perpendicular to said fixed plane, means shiftably supporting said platform in said bed for reciprocating movement substantially perpendicular to and alternately on opposite sides of the fixed plane of said feeding element work engaging surfaces, and means for imparting reciprocating movement to said work feeding element and to said work engaging platform in timed relation so that said work engaging platform is elevated above the plane of said feeding element work engaging surfaces during the nonfeedin-g reciprocatory movement of said work feeding element.

2. A work feeding mechanism as set forth in claim 1 in which said work feeding element comprises a feed dog.

3. A work feeding mechanism as set forth in claim 2 in which said feed dog work engaging surfaces comprise spaced work engaging bars, and in which said work en gaging platform is interposed between the spaced work engaging bars of the feed dog.

4. A work feeding mechanism as set forth in claim 1 in which the sewing machine bed is formed with an aperture within which said work feeding element and said work engaging platform are disposed, and in which a cover plate slidably constrained on said sewing machine I bed retractably closes said aperture, and said cover plate being formed with a slot embracing with slight clearance at least three sides of said work feeding element when said opening in said sewing machine bed is closed by said cover plate.

5. A work feeding mechanism as set forth in claim 1 in combination with a thread pull-off device comprising a thread pull-off lever including a lever arm formed with a thread guiding aperture, means pivotally supporting said thread pull off lever on said means shiftably supporting said platform in said bed, spring means biasing said thread pull off lever in one direction about said pivotally supporting means, and a stop fixed on said sewing machine bed and engaging said lever arm in opposition to said spring means to oscillate said lever arm always in a direction opposite that of the movement of said means shiftably supporting said platform.

References Cited UNITED STATES PATENTS 1,432,084 10/ 1922 Nielsen 112-203 1,526,937 2/ 1925 Sharaf 112203 2,197,255 4/1940 Kucera 112214 2,892,427 6/1959 Winberg 112203 X 3,164,113 1/ 1965 Ketterer 112-242 FOREIGN PATENTS 544,068 6/ 1956 Italy.

ALFRED R. GUEST, Primary Examiner US. Cl. X.R. 

